1. Field of the Invention
The present invention relates to a clamping apparatus with a datum function and more particularly to an apparatus for accurately aligning a work pallet or the like movable member with a reference member such as a table of a machining center and fixing it thereto in such an accurately aligned state.
2. Explanation of Related Art
There is a conventional example of the clamping apparatus of this kind disclosed in Japanese Patent Public Disclosure No. 11-10468. The conventional technique is constructed as follows.
A reference member has a supporting surface formed with a fitting straight hole. A retracting nipple fixed to a movable member has a flange fitted into the straight hole. Thus the straight hole has an axis made coincident with an axis of the nipple. Thereafter, the retracting nipple is pulled, thereby fixing the movable member to the reference member.
However, the conventional technique has the following problem.
In order to smoothly attach the movable member to the reference member, it is required to provide a diametrical fitting gap between the fitting straight hole and the flange. The existence of the fitting gap decreases the aligning accuracy of the both members.
The present invention aims at making it possible to smoothly attach the movable member to the reference member and to accurately align the both members with each other.
In order to accomplish the above aim, the present invention has constructed a clamping apparatus in the following manner, for example, as shown in FIGS. 1 to 3 or in FIG. 4.
The clamping apparatus aligns a movable member (M) with a reference member (R) and fixes a supported surface (T) of the movable member (M) to a supporting surface (S) of the reference member (R). The supported surface (T) of the movable member (M) is opened to provide a positioning hole 12, within which the movable member (M) is provided with a pull rod 13 substantially coaxially with the positioning hole 12. The reference member (R) projects an annular plug portion 21 which is inserted into an annular space defined between the positioning hole 12 and the pull rod 13. Arranged between the plug portion 21 and the positioning hole 12 is a shuttle member 23 which diametrically expands and contracts. The shuttle member 23 is supported by one of the plug portion 21 and the positioning hole 12 axially movably within a predetermined range and is able to make a tapering engagement with the other. The shuttle member 23 has a tapered surface 28 which is formed so that it narrows toward an inner portion of the positioning hole 12. The shuttle member 23 is urged by a resilient member 24 in such a direction that the tapering engagement is made tightly. The plug portion 21 has a cylindrical hole 21a, into which a transmission sleeve 31 is axially movably inserted. The transmission sleeve 31 has a cylindrical hole 31a which can receive an engaged portion 13b of the pull rod 13. The engaged portion 13b engages with and disengages from an engaging member 34, which is supported by the transmission sleeve 31. The reference member (R) is provided with a supply port 41 for cleaning fluid. A flow passage 43, 45 is formed in at least one of a space defined between the cylindrical hole 21a of the plug portion 21 and an outer peripheral surface 31b of the transmission sleeve 31, and a space inside the cylindrical hole 31a of the transmission sleeve 31. The flow passage 43, 45 communicates with the supply port 41.
The present invention operates, for example, in the following manner.
When clamping the movable member to the reference member, first, the movable member automatically makes an aligning movement owing to a guiding action of the tapered surface of the shuttle member. Then the positioning hole of the movable member has its axis made accurately coincident with an axis of the plug portion of the reference member. Next, the shuttle member compresses the resilient member and it moves axially. The movable member has its supported surface received by the supporting surface of the reference member and the shuttle member is closely attached to the positioning hole and the plug portion. Thus the movable member is constrained via the shuttle member by the plug portion as well as by the supporting surface. As a result, the transmission sleeve pulls the movable member through the engaging member and the pull rod, thereby allowing the movable member to be precisely and strongly positioned and fixed to the reference member.
According to the present invention, the tapered surface of the shuttle member can make an aligning guide of the movable member, so that the movable member can be smoothly attached to the reference member. Further, differently from the above-mentioned prior art, the present invention can remove the diametrical fitting gap defined between the members to be connected. This makes it possible to align the reference member with the movable member with a high accuracy. Besides, cleaning fluid discharged from the foregoing flow passage can clean an engaging gap and a contact gap formed between the reference member and the movable member, which results in the possibility of preventing a misengagement between the both members.
The present invention includes the following clamping apparatus.
For instance, as shown in FIGS. 1 to 3, the shuttle member 23 has an inner peripheral surface formed by a straight surface 27 and has an outer peripheral surface defined by the tapered surface 28. The straight surface 27 is supported by the plug portion 21 axially movably. The tapered surface 28 makes a tapering engagement with the positioning hole 12. On an outer periphery of the plug portion 21, the reference member (R) is formed with an annular attaching groove 29, into which the resilient member 24 is inserted and the shuttle member 23 has its base portion fitted.
According to this invention, the reference member is equipped with the shuttle member. Therefore, in the case where a number of movable members are attached to and detached from one reference member, the equipped shuttle members are reduced in number to result in the possibility of forming a clamping system simply. In addition, the resilient member is inserted into the attaching groove and the shuttle member has its base portion fitted thereinto. This can prevent chips or the like foreign matters from invading the attaching groove. Accordingly, the shuttle member can smoothly operate over a long period of time.
The present invention further includes the following clamping apparatus.
The supply port 41 for cleaning fluid communicates with the attaching groove 29. According to this invention, even if chips or the like foreign matters have invaded the attaching groove, the cleaning fluid can clean out the foreign matters. Therefore, the shuttle member can smoothly operate over a longer period of time.
The present invention still further includes the following clamping apparatus.
For example, as shown in FIG. 2, when driving the transmission sleeve 31 for unclamping, a leading end of the transmission sleeve 31 pushes at least one of the pull rod 13 and a top wall 12a of the positioning hole 12. This forms an engaging gap (xcex1) on the tapered surface 28 of the shuttle member 23 and defines a contact gap (xcex2) between the supporting surface (S) and the supported surface (T). This invention can offer an advantage that the movable member can be easily removed from the reference member owing to the existence of the engaging gap and the contact gap.
The present invention also includes the following clamping apparatus.
The pull rod 13 is supported by the movable member (M) diametrically movably within a predetermined range. In this case, when attaching the movable member to the reference member, even if the axis of the plug portion somewhat misaligns with the axis of the positioning hole, this misalignment can be absorbed by a diametrical movement of the pull rod made through an insertion resistance produced when the pull rod is inserted into the cylindrical hole of the transmission sleeve. This enables the pull rod to be smoothly inserted into the cylindrical hole of the transmission sleeve. As a result, the tapered surface of the shuttle member can smoothly make the aligning guide of the movable member.
Moreover, in order to accomplish the above object, the present invention has constructed a clamping apparatus in the following manner, for example, as shown in FIGS. 1 to 3 or in FIG. 4.
The clamping apparatus aligns a movable member (M) with a reference member (R) and fixes a supported surface (T) of the movable member (M) to a supporting surface (S) of the reference member (R). The supported surface (T) of the movable member (M) is opened to provide a positioning hole 12, within which a pull rod 13 is supported by the movable member (M) diametrically movably within a predetermined range. The reference member (R) projects an annular plug portion 21 which is inserted into an annular space defined between the positioning hole 12 and the pull rod 13. Arranged between the plug portion 21 and the positioning hole 12 is a shuttle member 23 which diametrically expands and contracts. This shuttle member 23 is supported by one of the plug portion 21 and the positioning hole 12 axially movably within a predetermined range and can make a tapering engagement with the other. The shuttle member 23 has a tapered surface 28 which is formed so that it narrows toward an inner portion of the positioning hole 12. The shuttle member 23 is urged by a resilient member 24 in such a direction that the tapering engagement is made tightly. The plug portion 21 has a cylindrical hole 21a into which a transmission sleeve 31 is axially movably inserted. The transmission sleeve 31 has a cylindrical hole 31a which can receive an engaged portion 13b of the pull rod 13. The engaged portion 13b engages with and disengages from an engaging member 34, which is supported by the transmission sleeve 31.
The foregoing invention operates, for example, in the following manner.
When clamping the movable member to the reference member, even if the axis of the plug portion somewhat misaligns with the axis of the positioning hole, this misalignment can be absorbed by the diametrical movement of the pull rod made through the insertion resistance produced when the pull rod is inserted into the cylindrical hole of the transmission sleeve. This enables the pull rod to be smoothly inserted into the cylindrical hole of the transmission sleeve. Next, the movable member automatically makes the aligning movement owing to the guiding action of the tapered surface of the shuttle member. Thus the positioning hole of the movable member has its axis made precisely coincident with the axis of the plug portion of the reference member. Subsequently, the shuttle member compresses the resilient member and it moves axially. The movable member has its supported surface received by the supporting surface of the reference member and the shuttle member is closely attached to the positioning hole and the plug portion. This constrains the movable member via the shuttle member by the plug portion as well as by the supporting surface. As a result, the transmission sleeve pulls the movable member through the engaging member and the pull rod, thereby allowing the movable member to be precisely and strongly positioned and fixed to the reference member.
According to the foregoing invention, the diametrical movement of the pull rod absorbs the misalignment and the tapered surface of the shuttle member can make the aligning guide of the movable member. Therefore, the movable member can be smoothly attached to the reference member. Further, differently from the prior art, the present invention can rid the diametrical fitting gap between the members to be connected, which results in the possibility of aligning the reference member with the movable member with a high accuracy.